1. Field of the Invention
The invention pertains to an x-ray examination apparatus, including an x-ray source, a scattered-radiation grid, an x-ray detector for converting x-ray intensities constituting an x-ray image into a video signal containing information for producing a visible image, which x-ray examination apparatus also includes means for correcting scattered-radiation effects in an x-ray image.
2. Description of the Related Art
An x-ray examination apparatus of said kind is described in the European Patent Application EP 0 358 268.
In the known x-ray examination apparatus, a digital image signal originating from the x-ray detector is converted into an image matrix of intensity values. By convolution of the image matrix with a point spread function a transformed image matrix is formed. A scatter image matrix is formed by multiplication of each matrix element of the transformed image matrix by a weighting factor. For each matrix element of the image matrix a relevant weighting factor is in fact the ratio of a scattered intensity and of a detected intensity. It was recognised in the cited reference that weighting factors are functions of intensity values of the matrix elements of the transformed image matrix. Finally, a corrected image matrix is formed by subtracting matrix elements of the scatter image matrix from corresponding matrix elements of the image matrix.
The x-ray examination apparatus as disclosed in the cited reference has inter alia as a drawback that weighting factors required are co-determined by imaging parameters of the x-ray examination apparatus. Employing a multitude of sets of weighting factors or simple parametrisations of weighting factors yields only a partially satisfactory solution to this problem.